Coke oven doors for horizontal coke ovens have been a source of air leakage during the coking cycles. Each horizontal coke oven has two doors. One door is located on a coal charging side of the oven and a second door is located on a coke discharge side of the oven. Each of the doors is made of a combination of refractory and metal and is very large and heavy. The doors are required to close the oven to maintain the heat inside the coke ovens which may range from about 1000° to about 1500° C., and to maintain a negative pressure inside the oven. A negative pressure is required to move flue gases and combustion products away from the coke bed in the oven.
Since the ovens operate under a negative pressure, it is important that both the charging door and the coke discharge door remain closed as tightly as possible, and that the doors remain tightly closed throughout the coking cycle. A tightly closed door means that the door is held tightly against the oven door jamb, lintel, and sill plate. Loose doors allow excessive air infiltration which can result in poor product quality or low product yields. Excess air entering the oven can come in contact with very hot coke (1000+° C.). Once contact is made, the air bums the coke product thereby reducing its value and leading to product yield loss.
Conventional door latches used to maintain the doors in a closed relationship with the coke ovens consist of cam latches that are manually adjusted. The cam latches engage a backside of a front flange of a beam which is disposed on each side of the oven door. There are typically four cam latches per door.
Door latch closing requires that a worker apply force to a wrench that is used to rotate and tighten the cam latches. Such force may lead to back strains and other injuries. Furthermore, a worker can apply only about 600 kilograms of force to each cam latch. This amount of force may not be sufficient to overcome slight irregularities, such as warping, bending, and solids buildup, of either the door frame or the door jamb. Accordingly, the doors may not be closed as tightly as necessary to reduce or prevent excess air infiltration into the oven.
During a 48 hour coking cycle there are small movements of the oven relative to the door. These movements are a result of differential thermal expansion. Such movements have a tendency to make the cam latches rotate slightly and become loose. Typically about 25 to 50 percent of the cam latches become loose during a coking cycle. Accordingly, significant manpower is required to monitor and adjust the cam latches for efficient coke oven operation.
Accordingly, there is a need for a door latch system that is less prone to movement or loosening and that can be positioned automatically rather than manually during an oven door closing operation.